How am I using factors which are not feasible when there is practically no way to generate gravity, much less have an element which can factor into creating it. There is no known way to generate gravity at will, however there is a known way to fly at over Mach 7. I don't see how creating your own gravitational pulls would be any more reasonable than flying in a slightly denser atmosphere at Mach 7. Hell, you don't even know if the planet even has a greater gravitational pull, maybe your Gravitanium has forgeted up the gravity, causing the atmosphere to be less dense. Maybe it was never denser than Earth's atmosphere at all, it could always have never gotten that much gas. There are hundreds of factors that you, yourself, are not factoring in for the possibility of a plane attaining Mach 7 speeds, and you pull miracle matter our of your ass.
Bull to the stuff.